final aListOfStrings2 = ['one', 'two', 'three'];
final aSetOfStrings2 = {'one', 'two', 'three'};
final aMapOfStringsToInts2 = {
  'one': 1,
  'two': 2,
  'three': 3,
};

final aListOfInts2 = <int>[];
final aSetOfInts2 = <int>{};
final aMapOfIntToDouble2 = <int, double>{};

// 在使用子类型的内容初始化列表，但仍希望列表为 List <BaseType> 时，指定其类型很方便：
// final aListOfBaseType = <BaseType>[SubType(), SubType()];

// Assign this a list containing 'a', 'b', and 'c' in that order:
final aListOfStrings = ["a", "b", "c"];

// Assign this a set containing 3, 4, and 5:
final aSetOfInts = {3, 4, 5};

// Assign this a map of String to int so that aMapOfStringsToInts['myKey'] returns 12:
final aMapOfStringsToInts = {"myKey": 12};

// Assign this an empty List<double>:
final anEmptyListOfDouble = <double>[];

// Assign this an empty Set<String>:
final anEmptySetOfString = <String>{};

// Assign this an empty Map of double to int:
final anEmptyMapOfDoublesToInts = <double, int>{};
